Picornaviruses cause diseases typified by polio, colds, hepatitis, and foot-and-mouth diseases. Sequences of these viruses have been examined for relationships among them and to other known and hypothetical proteins. Secondary structures of the RNAs have been found to vary in correlation with pathological and sequence differences. Adenoviruses are studied with a goal to understanding early events in virus replication wherein the cell's metabolism is subverted to viral functions, and late events during which assembly and morphogenesis occurs. Early viral proteins, whose existence was known from biochemical studies, have been analyzed by comparing their sequences to cellular proteins of known function. Techniques of biochemistry, virology, electron microscopy and computer analysis are used to study sequences of picornaviruses, adenoviruses, human immunodeficiency viruses and genes. Analyses of proteins and nucleic acids have been developed and implemented. Graphic representations revealing homology, and reverse complementarity are coupled with numerical methods to aid the prediction of secondary structure, splicing, promoters, and recombination in nucleic acid molecules. Programs are developed locally and elsewhere for application on Cray XMP, VAX and graphic workstations to perform sequence analysis and structure predictions. Methods to assess the significance of predictions use Monte Carlo simulations, evolutionary comparisons and biochemical data. Protein secondary structure is being predicted from amino acid sequences. New sequences are compared with computerized databases to detect relationships with known proteins.